SMSL R100 combines AD1861-J R2R conversion with browser-based parametric EQ

The SMSL R100 is a desktop R2R DAC centered around two Analog Devices AD1861-J converter chips, combining resistor-ladder digital-to-analog conversion with high-resolution PCM and DSD support, browser-based parametric EQ, and dedicated digital filtering. USB playback extends to 32-bit/768kHz PCM and DSD up to 22.5792MHz, while optical and coaxial inputs support PCM up to 24-bit/192kHz and DSD64 through DoP. Balanced XLR and single-ended RCA outputs allow the R100 to integrate with desktop systems, powered speakers, and conventional hi-fi amplification.

Dual AD1861-J resistor-ladder conversion

Digital-to-analog conversion is handled by a pair of Analog Devices AD1861-J DAC chips. The AD1861 uses a resistor-ladder architecture, converting digital samples through precisely weighted current paths rather than the noise-shaping approach used by many modern delta-sigma converters.

SMSL pairs the two converters with a proprietary de-glitch circuit. R2R conversion can produce brief switching transients as multiple ladder elements change state between sample values, and the additional circuitry is designed to suppress these conversion glitches along with associated distortion, digital noise, and unwanted artifacts.

PCM and DSD playback up to 32-bit/768kHz

Through USB, the R100 accepts PCM streams up to 32-bit/768kHz and DSD up to 22.5792MHz. SMSL also implements a dedicated DSD conversion algorithm that allows DSD source material to be processed through the R2R conversion architecture.

The optical and coaxial S/PDIF inputs support PCM resolutions up to 24-bit/192kHz. DSD64 is also supported over these connections using DoP, which packages the DSD data inside a PCM-compatible transmission frame without converting the source into PCM.

Web-based parametric EQ

The R100 includes a browser-accessible parametric EQ system, allowing frequency-response adjustments without installing a dedicated desktop application. Parametric EQ provides control over specific frequency regions rather than applying a fixed tonal preset, making it suitable for correcting loudspeaker or headphone response, compensating for room interactions, or applying a preferred target curve.

Three operating modes are provided: Direct EQ, EQ1, and EQ2. Parameters can be stored for later recall, allowing multiple correction or tuning profiles to remain available without rebuilding the filter configuration for each use.

Dedicated S/PDIF digital filtering

Optical and coaxial signals are processed through SMSL's self-developed high-precision S/PDIF digital filter algorithm. The processing is designed to reduce the influence of incoming clock jitter and maintain stable digital transmission before conversion, addressing timing variation in the recovered S/PDIF data stream.

This processing stage is separate from the AD1861-J conversion itself and is intended to provide the R2R section with a more consistently timed digital signal when the DAC is used with transports, streamers, televisions, and other optical or coaxial sources.

Balanced XLR and RCA analog outputs

The rear panel provides both balanced XLR and single-ended RCA outputs. The XLR connection is rated at 3.5Vrms, while the RCA output is rated at 1.75Vrms. Both have a specified output impedance of 33 ohms, providing a low source impedance for connection to downstream preamplifiers, integrated amplifiers, headphone amplifiers, and powered speaker inputs.

SMSL uses gold-plated signal connectors across the input and output connections. The plating provides resistance to surface oxidation and corrosion, helping the electrical contact surfaces remain stable through repeated connections and long-term use.

Measured line-output performance

SMSL specifies overall THD+N at 0.003%, while supplied Audio Precision APx555 B measurements show approximately 0.0025% THD+N from the balanced line output. THD+N combines harmonic distortion with residual noise into a single measurement, providing an indication of unwanted signal content relative to the fundamental output.

CNC-machined aluminum construction

The R100 uses an aluminum chassis produced through integrated CNC machining followed by grinding and polishing. The rigid enclosure provides a stable mechanical housing for the internal converter, processing, and analog circuitry while remaining compact enough for desktop systems and equipment racks.

Two transparent viewing panels are integrated into the top of the chassis, exposing sections of the internal hardware and component layout. The windows make the dual-converter design and surrounding circuitry visible without opening the enclosure.

Computer and digital-source compatibility

USB operation is supported on Windows 7, 8, 8.1, 10, and 11 with the appropriate driver. macOS 10.6 or later and Linux systems are supported without a dedicated driver, giving the R100 broad compatibility with computer-based playback systems.

Alongside USB, the optical and coaxial inputs allow the same DAC to be used with dedicated digital transports and other S/PDIF-equipped sources, with the input-specific resolution limits and DSD64 DoP support retained across those connections.

Availability

The SMSL R100 is now available on Apos.